Video recording and playback devices are widespread in use and are operable in a record mode to record broadcast data on a recordable medium. In a playback mode, the video recording and playback device is operable to couple the recorded broadcast data to a display device where it may be viewed at the convenience of the viewer. The use of video recording and playback devices has enabled viewers of broadcast data to control their viewing habits.
In the past, it was necessary for a viewer to manually stop and restart the record mode to prevent the recording of undesired portions of broadcast data such as advertising commercials which are typically interspread throughout desired program data. In order to provide an additional degree of convenience, the video equipment industry has attempted to provide devices that control the video recording and playback device in its record mode to automatically inhibit the recording of unwanted advertising commercials.
One technique used in the past to detect commercials was the monitoring of the amplitude of the video and audio signal of the broadcast data for a drop of the video signal to a black level and a drop of the audio signal to a zero sound level. One disadvantage, however, on relying on a drop of the video and audio signals to indicate the broadcast of a commercial is that video and audio signals may also drop during the broadcast of program data, thus falsely indicating the broadcast of a commercial. This produces the undesirable result of taking the video recording and playback device out of the record mode during the broadcast of program data.